In a recent wiring technology, copper lines are replacing aluminum lines to improve performance of a semiconductor device. In a manufacturing process of the semiconductor device, a technology for forming a copper film on a surface of a semiconductor wafer (hereinafter, referred to as a “wafer”) is important. A chemical vapor deposition method (hereinafter, referred to as “CVD”) using a copper organic compound as a material has been known as one of technologies for forming a copper film on the wafer.
When a copper film is formed on the wafer by using CVD, a copper organic compound, e.g., Cu(hexafluoroacetylacetonate)trimethylvinylsilane (hereinafter, referred to as “Cu(hfac)TMVS”) serving as a source gas is supplied to a processing chamber in a vacuum state, and the Cu(hfac)TMVS is thermally decomposed on the heated wafer to form the copper film on the wafer.
However, since copper atoms tend to be diffused into the insulating film, the copper film is mostly formed on a diffusion barrier film (hereinafter, referred to as a “base film”) called a barrier metal, which is formed in advance on the substrate, instead of being directly formed on the wafer.
The base film employs titanium, tantalum, nitride thereof or the like. However, the barrier metal of the base film reacts with an organic material from the copper organic compound, thereby producing organic impurities at an interface between the copper film and the barrier metal.
In this case, adhesiveness between the base film and the copper film is weakened due to an organic impurity layer and a resistance between an upper copper line and a lower copper line increases. Accordingly, electrical characteristics deteriorate or the copper film is peeled off while processing the wafer, resulting in a reduction in production yield. Further, since the organic impurity layer has poorer wettability than the base film, copper can be easily aggregated to thereby reduce buriability of the copper in a trench having a high aspect ratio, thereby causing a formation defect of the copper line.
In order to solve the problem that the adhesiveness between the copper film and the base film is reduced due to formation of the organic impurity layer, Japanese Laid-open Application No. 2002-60942 (see, particularly, paragraphs [0037], [0038] and [0057]) discloses a technology using water vapor. In accordance with the technology disclosed in the above-mentioned document, water vapor is supplied in advance to the processing chamber containing the wafer, and both the water vapor and Cu(hfac)TMVS are supplied to the processing chamber for, e.g., 0.5 second. Then, only the supply of water vapor is stopped to prevent formation of the organic impurity layer, thereby obtaining the copper film having improved adhesiveness to the base film.
However, in the CVD using Cu(hfac)TMVS as a material, it is known that the water vapor causes a demerit of abnormal growth of the copper film in a needle shape though it prevents formation of the organic impurity layer. From this point, in the technology disclosed in the above-mentioned document, since the water vapor still remains in the processing chamber even though the supplies of these gases are stopped, it is difficult to immediately stop the abnormal growth of the copper film. In this case, since a gap develops between the base film and the copper film, it is difficult to improve adhesiveness.